Propeller pitch governor



Mald'l 20, 1951 H. CARSON ET AL PROPELLER FITCH GOVERNOR s sheetssheet 1 Filed Oct. 25, 1945 INVENTORS HOWARD CARSON ./MEs M. lef/r B m O .m

March 20, 1951 H. CARSON ET AL 2,545,684

PROPELLER FITCH GOVERNOR Filed Oct. 25, 1945 5 Sheets-Sheet 2 IN V EN TORS Hana/w @Ansa/v By JA M55 W /QHT H. CARSON ET AL PROPELLER PITCH GOVERNOR l March 20, 1951 3 Sheets-Sheet 5 Filed Oct. 25, 1945 SM H MW 3 E W /o my. n a

kI increases for any reason then the piston 2| will be forced downward more to open the port I9 to a greater extent, thereby relieving that pressure increase. Similarly, if there is a fall of pressure in pipe l5 for any reason, the valve 2| moves upward and closes off the port I9 so that there is less drain which allows the pressure to build up in pipe I6. At an increase of propeller speed more centrifugal force is assisting the spring 22 to such an extent that the port I9 tends to close a little more and the port il to open a little wider to admit more pressure opposing the spring and centrifugal force. For a decrease in propeller speed the opposite obtains.

Cylinder 20 is connected by pipe 25 with a source of pressure provided by a pump 25 of relatively low capacity, and by pipe 2l with a selector valve F comprising a cylinder 29 having ports 28, 3| and 32 controlled by a piston 3B under control by pressures at opposite ends of the cylinder and by a spring 33. Port 3| is connected with an auxiliary source of pressure provided by a pump or pumps 34 of relatively high capacity.

The left end of cylinder I5 of servo A is connected by pipe 3B with a pipe 3l connected with a port 38 in cylinder 29 and with a cylinder 45 of a valve C receiving a dash pot piston 4| having leak notches 42 and connected by a rod 43 with a small piston 44 received by a cylinder 45. Piston 44, which controls the opening and closing of a bleed port 4l, is under control by centrifugal force acting in the direction of arrow 44a and by pressures above and below it and by a spring 46. Thus, the force of pressure in cylinder 45, the force of spring 45 and centrifugal force acting on the rod 43 tend to move it upward in the direction of arrow 44a and in opposition to the force of pressure in the cylinder 45 acting downwardly on the end of the small piston 44. When the propeller is on speed and the piston I4 of torque unit A should remain stationary, the pressure at the left lof piston I4 should be limited to a value such that all forces acting on the piston I4 (including centrifugal blade torque) will be in balance. As will be explained later, when on-speed, the unit pressure below piston 44 is substantially lower than the unitpressure above it. The total pressure above piston 44 overcomes the spring 45 and the action of centrifugal force sufficiently to cause piston 44 to open the bleed port 41 sufficiently to limit the pressure to the left of piston I4 to such value that the piston I4 will be in balance. As propeller speed increases, centrifugal force acting on piston 44 increases and greater pressure is required to effect opening of bleed port 4l. Hence the pressure to the left of piston I4 increases. As stated before, as propeller speed increases, greater pressure is required to effect opening of bleed port I9 of unit B. Hence the pressure to the right of piston I4 increases. The pressure increases on both sides of 'piston I4 are cornmensurate. That is, for each position of piston I4 corresponding to a different speed-setting of the apparatus, when the apparatus is in the onspeed status, the piston will be held stationary by higher pressures when the propeller speed is high and by lower pressures when the propeller speed is low.

Cylinder 40 is connected by pipe 48 with a cylinder 5I) of a speed responsive valve-unit D; and pipe 48 is connected by pipe 48a with the right end of cylinder 29. Cylinder 50 receives the lands 5| and 52 of a valve 53 connected with a lever 54 urged against an adjustable fulcrum 55 by a spring 55. Valve 53 is radially movable relative to the axis of rotation of the propeller hub in response to change of propeller speed and is therefore under control by centrifugal force acting in the direction of arrow 53a and by the spring 55, the effect of which is varied by moving the fulcrum 55 horizontally as viewed in the drawing. Land 5| controls a port 51 connected by a pipe 49 with the cylinder 45, and a port 58 connected by a pipe 59 with a cylinder 50 of a shuttle valve E. Land 5| and ports 5l and 58 have the same width. Land 52 controls a port 56 which is so spaced with respect to ports 5l, 58 and the lands 5|, 52 that the port 55 is partly open to drain when the ports 5l, 55 are completely covered by the land 5 I.

Shuttle'valve E comprises cylinder 60 receiving a piston valve 5| having notched end lands 62 controlling a port 63 connected by pipe 64 with the left end of cylinder 29 of selector valve F. The right end of cylinder 55 is connected by pipe 65 with the port 5E of cylinder 55 of speed responsive valve D.

Fig. l shows an on-speed position. Pump 26 is connected with ports 23, 24, il and 33. Upper end of cylinder 29 has pressure which balances spring 22. Piston 2| tends to maintain pressure (constant at a given propeller speed) in right end of servo cylinder I5 and upon the right face of piston i4 in the direction tending to decrease pitch of propeller blade Il). When on speed, the valve land 5I vibrates closely adjacent to ports 5l and 53 substantially as disclosed in the U. S. Patent 2,407,791 to Martin et al., of September 17, 1946, so that ports 51 and 55 receive a pressure substantially less than the pressure in pipe 48, cylinder 49 and pipe 3l. That is because the valve land 5| in vibrating alternately opens 51 and 5S to pump pressure from 48 and to drain out of the top end of cylinder 55. yAt the same time land 52 is vibrating with respect to the port 55 but only to such a degree that the port 56 remains more or less open to drain from the bottom of the cylinder 59 which allows the passage 65 to remain at zero pressure. Though the pressure below piston 44 is substantially lower than the pressure above it when the apparatus is in the on-speed status, the valve unit C can still control the bleed port 4l so as to maintain at the left of piston I4 the pressure required to hold the piston I4 stationary. Because the valve 53 has a vibratory controlling action, the pressure in cylinder 45 of valve C may fluctuate; 'but these fluctuations do not produce appreciable fluctuations of the valve 44 due to the damping action of the notched dash pot piston 4|.

Since port 55 is open to drain, pipe 55 has zero pressure. The pressure in port 56 is communicated by pipe 59 to the left end of cylinder 55 of shuttle valve E. Valve 6l therefore moves right to the position shown in Fig. l. Pressure in left end of cylinder 69 is communicated to the left end of cylinder 29 of selector valve E through the notches in left land 52 of valve 6| and the pipe 64. Since the pressure in pipe 59 is less than the pump pressure in pipes 48 and 48a, the pressure in right end of cylinder 29 is greater than the pressure in the left end of said cylinder plus the pressure of spring 33. Piston 30 of valve F remains in the position shown in Fig. l, and pump 34 remains connected with drain.

Fig. 2 shows the condition of the apparatus Whenthere is a substantial overspeed. Piston 53 has. moved up a substantial distance to delinitely connect the source. pressure from 48 'with ports 51 and 5.8.v The port 66 is now more widely opened to drain which results in no pressure in 65, while the pressure in pipes 49 and 59 becomes equal to the pressure. in pipes 48 and 48a, PlstonV 44 rises to close port 41 and the pressure rises the left end of cylinder l5 to a value Sueent to effect lincrease of blade pitch. For any propeller speed. whenever there is a Substantial over-speed error demanding pitch increase, the action of valve C is immediately modiiied t effect a pressure increase at the pitch-increasing side of the piston VI4 which overbelances the pressure at the right of piston I4, Since 48a and 59 are now connected the pressure rises in the left end of cylinder 29 and becomes equal to the pressure inthe right end of cylinder 29. Therefore the spring 33 moves the piston 30 right to block the. drain 32 and to connect pump 34 with pipe 25. The total output of both pumps causes a rapid increase in pitch in order to reduce the overspeed. As piston i4 moves right the pressure in the upper end of cylinder 2t increases to cause piston 2| 'to move down to open the discharge hole I9.

Fig. 3 shows the condition of the apparatus when there is a substantial underspeed. Piston 53 has moved down a substantial distance below equilibrium position of Fig. 1 so that port 66 is closed to drain and opened to the pressure in 48 and sc that ports 51 and 58 are both open to drain at the top end of the cylinder D, Cylinder 45 hasno pressure.A Pressure in cylinder 49 above piston 44 moves it down to open port 41 and the pressure in left end of cylinder l5 falls rapidly below the pressure in the right end of the cylinder. Piston I4 begins moving left and pressure above piston ZI of valve B falls and spring 22 moves the pistonZI from the position shown in Fig. l to the position shown in Fig. 3. PortY I1 is Open Wider and port 38 is closed. The right end of cylinder I5 receives the output of both pumps 26 and 34, and piston I4 moves left. For any Vpropeller speed, Whenever thereis a substantial under-speed error demanding pitch decrease, the action of valve C is immediately `modied by relieving pressure below piston 44,

so that piston 44 isV caused fully to open the bleed Y port 41 whereupon pressure to the left of piston I4 falls below pressure to the right of piston I4.

Again the piston 3l) of selector valve F moves right to the same position as shown in Fig. 2 because'the pressure in pipe 65 is the same as in pipe 48 and the pressures at both ends of the cylinder 29 are equal and spring 33 moves valve 30 to the position shown in Fig. 3.

From the foregoing it is apparent that the system of control includes a valve B serving as means to limit the pressure in the pitch-decreasing end of cylinder I5 to a value su'icient for decreasing the pitch. Valves D and C' provide means responsive to speed for controlling the pressure in the pitch-increasing end of the cylf inder I5. When on-speed, the pressure is that required to maintain the blade stationary. When overspeeding, the pressure at the left of piston' illsk of a duet' 'iconnected with .the pitchein-1 creasing end of cylinder I5. It has a pistonv valve 44 which is loaded by a spring .46 and by nydraulio loading (pressure below piston 44) to oppose opening of bleed port 41 by pressure in duct. When .there .is an overspeed error, valve D effects increase in the hydraulic loading of valve 44, and when there is an under-speed error, valve D eiects reduction of the hydraulic load- `ing of valve 44.

Valves D. E F provide Speeflferror celitrelled mea-ns for determining whether the large capacity pump shall be connectedwith the leigh pressure line 25. Valve F has a piston valve 3B which is controlled b y a spring and the differ.- ential of pressures in the ends of cylinder 29. Valve D controle this difierential. When on speed, the pressure. ign the left end of cylinder 29 is Such 10W value, that the pressure dllerential opposing the spring -33 exceeds the force of the spring. Hence valve 30 is positioned for drain.- ing the large capacity pump. When there is substantial overspeed or underspeed, the pres.- sure dilerential is practically zero; and spring 33 is effective to move the valve 3Q to position for connecting the large capacity pump with the high pressure line. Therefore the system provides hydraulic capacity for effecting the .correction of a substantial speed error; b ut when substantially cri-speed, Only the outputof the small pump is required.

A structural embodiment of the pre-Sent inE vention will now be described With reference to Figs. 4, 5 and 6. Fig.V 4 shows somewhat diagrammatically a type of blade angle adjusting torque unit such as disclosed in the patents to Blanchard and MacNeil, Nos. 2,307,101 and 2,307,102, issued January 5, 1943. Referring to Fig. 4, engine frame 10 supports an engine driven shaft 1I which supports and `drives a hub 12 providing bearings 13 for the roots of blades 14, each of which is attached to a ring 15 providing a bevel gear 16 meshing .with a master or equalizing gear l'l1 journaled in a bearing 18 provided by the hub 12. Each blade 14 is connected with a cylinder rotatably supported by a bearing 8I provided by the hub 12. Cylinder 80 has internal helical splines 82 mating with external helical splines 83 of a piston 84 reciprocable in the cylinder 80.' Piston 84 has internal helical splines mating with external helical splines 85 of a member 86 provided by the hub 12. Clinder -30 is closed at its inner end by the hub 12 and at its outer end by a cap 81. The inclinations of the helical splines are such that inward movement of the piston 8s effects pitch-increasing rotation of the blade 14. As shown in Figp, the hub 12 supportsV and drives a' plate 90 fastened to the hub by a tubular nut 9I threadedly engaging the hub at 92. Nut 91 is surrounded by annular members 93, 94 and which are fastened together in any suitable manner so as to provide in effect a single tubular member vmarked 95 in Fig. 4. To the plate 99 there is attached a cover IDE] which together with partsl,y 94 and 95 provide an annular chamber for containing hydraulic iiuid. Plate 99 and cover lill) 'provide Vbearings IDI and |92 respectvelv ,for supporting the parts 93 and 94. There is an Oil seal |03 between Part 83 and plate Si). and there iS an Oil seal |04 between part 95 and cover |100. Rotation of parts 93, 34 and 9 5 is prevented by providing part 95 (95 in Fig.

4) with a tang 96A Confined between brackets or more' gears 99l for driving oil pumps as shown in Fig. 4. Part 95 supports a ring gear |05 having an operating handle |06 and meshing with a plurality of small gears |91, each connected with a shaft |98 rotatably'supported by the part 94 (Fig. 6). Each shaft |98 is provided with screw threads |99 for engaging a groove control ring ||9 which receives a shoe attached to a carriage ||2 of Fig. 4 having rollers ||3 received by channel shaped guides H4 provided by the Valve body ||5 which provides the cylinder 59 of valve unit D. The roller 55 or valve unit D (Fig. 1) is carried by the carriage ||2. The various parts of units B, O and D and some of the oil passages of Fig. 1 are marked in Fig. 4 with reference numerals used in Fig. 1.

Fig. 5 shows an arrangement of the instruments of Fig. 1 upon the plate 99. In this figure, the instruments and ducts are marked as shown in Figs. 1, 2 and 3. Ducts I6 and 36 may be arcuate as shown in Fig. 5 and may be connected by branch passages with a plurality of torque units in the manner indicated in Fig. 4. Fig. 1 shows a single pump 34 of larger capacity than the pump 26. Fig. 5 shows two pumps 34 connected in parallel, each of which may have the capacity of the pump 26.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. Apparatus for controlling pitch of propeller blades comprising a servomotor having a cylinder and a blade rotating piston, a fluid pressure source, means for limiting the pressure in the pitch-decreasing end of the cylinder to avalue sufficient for decreasing blade pitch, a bleed port connected with the pitch-increasing end or the rcylinder, a valve ior controlling the port and urged by pressure in the pitch-increasing end of the cylinder toward port opening position,

means for opposing such movement of the valve including means for hydraulically loading the valve, and speed responsive means effective, `when on speed, to effect such hydraulic loading Ao the valve as to obtain a pressure in the pitch-- increasing end of the cylinder suiicient to hold the piston stationary, and eective, when there is over-speed or under-speed, to increase or de crease, respectively, the hydraulic loading of said valve.

2. Apparatus for controlling pitch -oi propeller blades comprising a servomotor having a cylinder and a blade rotating piston, a fluid pressure source, means for limiting the pressure in the pitch-decreasing end of the cylinder to a value sufficient for decreasing blade pitch, a bleed port connected with the pitch-increasing end of the cylinder, a piston valve for controlling the port, a cylinder for receiving the valve, a spring urging the valve toward port closing position, a pressure uid connection between the pitchdecreasing end of the servomotor cylinder and an end of the valve cylinder to provide pressure upon the piston valve to urge it toward port opening position, a pressure fluid connection between the source and the other end of the valve cylinder to provide a pressure upon the piston valve to urge it toward port closing position, and a speed responsive Valve for controlling the second mentioned connection. i

3. Apparatus for controlling pitch of propeller blades comprising a servomotor having a cylinder and a blade rotating piston, a iiuid pressure source, means for limiting the pressure in the pitch-decreasing end of the cylinder to a value suicient for decreasing blade pitch, a bleed port connected with the pitch-increasing end of the cylinder for limiting the pressure in the pitchincreasing end of the servo cylinder to a value sufficient for opposing decrease-pitch change during on-speed operation, means for controlling the port including a cylinder and a spring loaded piston valve means applying the fluid pressure source to one side of said spring loaded piston, and means for hydraulically loading the spring loaded piston in proportion to error Y of blade pitch for eecting diierential of pressures in the cylinder on opposite sides of the spring loaded piston, and speed responsive means for controlling the pressure differential.

4. Apparatus for controlling pitch of propeller blades comprising a servomotor having a cylinder and a blade rotating piston, a first fluid pressure pump, means responsive to speed-error for controlling the differential of pressure actting upon the servomotor piston, a second fluid pressure pump, a valve for controlling a connec tion between the outlet of the second pump and the outlet of the rst pump, a spring for moving the valve in the direction to connect the outlets of both pumps with the servomotor, fluid pres-l sure means for moving said valve in the other direction to disconnect one of the pumps from the servomotor, and means for controlling the fluid pressure means and operating when there is a substantial speed-error for reducing the efiectiveness of the huid pressure means whereby the spring is effective to move the valve in the rst mentioned direction.

5. Apparatus for controlling pitch of propeller blades comprising a servomotor having a cylinder and a blade rotating piston, a rst fluid pressure pump, means responsive to speed-error for controlling the differential of pressures acting upon the servomotor piston, a second fluid pressure pump, a valve for controlling a connection between the outlet of the second pump and the outlet of the first pump, a spring for moving the valve in the direction to connect the outlets of both pumps with the servomotor, fluid pressure means acting against the spring for moving the valve in the other direction to disconnect one of the pumps from the servomotor, a second iiuid pressure means for opposing the rst fluid pressure means, and speed-error responsive means for so controlling the second fluid pressure means that, when on speed, the force of the second iluid pressure means plus the force of the spring is less than the force of the first fluid pressure means and that, when there is a substantial speed-error, the force of the second uid pressure means is substantially equal to the force of the rst fiuid pressure means whereby the spring is eifective to move the valve in the first mentioned direction.

6. Apparatus for controlling pitch for propeller blades comprising a servomotor having a cylinder and a blade rotating piston, a first uid pressure pump for operating the servomotor, means responsive to speed-error for controlling the differential or" pressures acting upon the servomotor piston, a second iluid pressure pump, a piston valve for controlling the connection of the outlet of the second pump with drain or with the outlet of the first pump, a cylinder enclosing said valve, a spring for moving the valve toward position for connecting the outlet of'the second pump with the outlet of the rst pump, a pressure connection to an end of the valve cylinder for applying pressure to movethe valve against the action of the'spring to connect the outlet of the second pump with drain, a pressure connection to the other end of the valve cylinder for applying pressure in the opposite direction, and means for controlling the pressure last mentioned and operating upon substantial speederror` to reduce the pressure diierential to such low value that the spring moves the valve to connect the second pump outlet with the first pump outlet.

7. Apparatus for controlling pitch of propeller blades comprising a servomotor having a cylinder and a blade rotating piston, a fluid pressure source for application to both sides of said pis-Y ton, pressure limiting means for applying the source pressure to the decrease-pitch end of said cylinder and including a bleed port for reducing the limited pressure applied to a value sufficient for decreasing blade pitch, pressure control means for applying the source pressure to the increase-pitch end of said cylinder and including a bleed port for reducing the controlled pressure applied to a value suicient for increasing blade pitch, said limited pressure and controlled pressure being applied to opposite sides of the servor piston for effective opposition to piston movement during pitch maintained position, means hydraulically loading th pressure REFERENCES CITED The followingy references are of record in the le of this patent; Y

UNITED STATES PATENTS Number Name Date 2,112,965 Koster Apr,v 5, 1938 2,205,625 Mader June 25, 1940 2,257,126 Rindfleisch Sept. 30, 1941 2,307,849 Mullen Jan 12, 1943 2,310,261 Schwartzhaupt et al. Feb. 9, 1943 FOREIGN PATENTS Number Country Date 501,054 Great Britain Feb. 20; 1939 

